1. Field of the Invention
The present invention relates to methods and apparatus for inspection and/or review of semiconductor wafers and other manufactured substrates.
2. Description of the Background Art
Semiconductor manufacturing involves various processes. Common processes include those that form microscopic features on the substrate being manufactured. The microscopic features may comprise dielectric or metallic materials, for example.
Microscopic metal features may include plugs and lines and may be formed by dielectric etch, metal deposition and metal chemical mechanical polishing (CMP) processes. The detection of voids in such metal features is generally an issue of interest in integrated circuit chip manufacturing. However, detecting voids or other buried defects in microscopic metal features, particularly in metal plugs and other features that are less than a micron in width, is a very challenging task due to the hidden nature of these defects.